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Humanity’s Earliest Ancestor Is an Ancient Worm?

ICTMN Staff

3/5/12

Scientists say they’ve discovered mankind’s oldest ancestor—Pikaia gracilens. The rarely found 505 million-year-old fossil of a two-inch worm found only in the Burgess Shale fossil beds, located on a ridge between Mt. Field and Wapta Mountain in British Columbia, Canada’s Yoho National Park.

Charles Doolittle Walcott, a paleontologist who discovered the fossil bed in 1911, first described Pikaia as an annelid worm, which today includes leeches and earthworms.

But scientists have long suspected that Pikaia belonged to the chordate family, which today includes fish, amphibians, birds, reptiles and mammals.

In a study published March 5 in Biological Reviews, scientists say Pikaia had a notochord, which is a “flexible rod found in the embryos of all chordates—which goes on to make up part of the backbone in vertebrates,” says a press release from the Royal Ontario Museum (ROM), which conducted the study with the University of Toronto and the University of Cambridge in the United Kingdom.

One of the study’s authors, Jean-Bernard Caron, assistant professor of ecology and evolutionary biology at the University of Toronto and curator of invertebrate palaeontology at the ROM, said the notochords aren’t the most exciting part of the study—the discovery of myomeres, bands of muscles that are the precursors to a skeletal spine, are the real exciting part.

“The discovery of myomeres is the smoking gun that we have long been seeking,” said the study’s lead author, Professor Simon Conway Morris of the University of Cambridge, in the ROM release. “Now with myomeres, a nerve chord, a notochord and a vascular system all identified, this study clearly places Pikaia as the planet’s most primitive chordate. So, next time we put the family photograph on the mantle-piece, there in the background will be Pikaia.”

“It’s very humbling to know that swans, snakes, bears, zebras and, incredibly, humans all share a deep history with this tiny creature no longer than my thumb,” said Caron.

Though he told CP24.com that humans having evolved from the Pikaia is a “long shot.” He said the creature is a “very, very distant cousin” and that “we share the same genes… some of the basic features.”

The Burgess Shale was named a UNESCO World Heritage Site in 1981, 80 years after it became Yoho National Park—Yoho is “a Cree expression of awe and wonder that reflects the natural magnificence of the waterfalls, glaciers, and towering peaks around the Kicking Horse Valley,” says Parks Canada. There are 936 properties worldwide that are said to have “outstanding cultural value” by UNESCO.

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